Altec Lansing BB2001 Subwoofer for inMotion Speakers Compact subwoofer designed for portable inMotion speaker systems Adds serious bass to iM5, iMX2, iMT1, and XT2 audio systems 5.25-inch woofer delivers 40 Hz to 175 Hz frequency response Plugs into speaker system's Sub Out port; includes 3.5 mm stereo cable Measures 5.75 x 9.75 x 9.5 inches (W x H x D); 1-year warranty